Abstract

The atomization is a process widely used in aerospace, combustion, or thermal spray coating, and is controllable by adopting different fluids as well as by retrofitting nozzle geometry. Desired characteristics of atomized fluid radically depend on the application of the spraying process which could be achieved by the appropriate selection of the nozzle, as well as changing the operating conditions. The objective of this study is experimental investigation of the atomization process by an effervescent nozzle for a variety of fluids where there is a lack of experimental knowledge.
Four different liquids were taken: distilled water, pure glycerol, water-glycerol aqueous solution and suspensions. The suspension is prepared by an optimized proportion for each case in order to mitigate the sedimentation and clogging of suspended beads. We determined the properties of the atomized fluids in accordance to the commonly used quantities in practical applications. Beside the rheology analyses of the fluids, three types of characterization experiments such as shadowgraphs, PIV and PDPA were conducted. Firstly, shadowgraphs were captured and the overall structures of spraying regions were observed. Accordingly, PIV and PDPA data were provided, consisting of a velocity profile in different operating conditions as well as distributions of a droplets’ diameter.
The main characteristics of atomized fluids are velocity profiles, droplet size distributions, spray cone angle, and breakup lengths. These characteristics with dimensionless variables, namely Gas to Liquid Ratios (GLRs), are calculated and compared. It was found that varied values of dynamic viscosities and surface tension values have effects on the atomization affecting breakup lengths and droplet size distributions. Various recommendations were provided regarding the experimental results and future works.